In the top of a double boiler over gently simmering water, melt the chocolate, stirring occasionally. Remove from the heat. In a bowl, stir together the sugar and the water until all granules of sugar have dissolved. Stir in the dissolved sugar mixture and the corn syrup thoroughly into the chocolate until all are absorbed. Return the pan to low heat and stir in the margarine and the vanilla. Serve at once or cool, cover, and refrigerate in 1 cup containers. Reheat to the desired temperature before serving.
c.1997, M.S. Milliken & S. Feniger, all rights reserved